1. Field of the Invention
The present invention relates to a method of manufacturing a magnetic recording medium that is used in a hard disk device (HDD) or the like, and a magnetic recording and reproducing device.
Priority is claimed on Japanese Patent Application No. 2012-010399, filed on Jan. 20, 2012, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, an application range of a magnetic recording device such as a magnetic disk device, a flexible disk device, and a magnetic tape device has been widely used, the importance thereof has been increased, and recording density of a magnetic recording medium that is used in these devices has been significantly improved. Particularly, since an MR head or a PRML technology was introduced, surface recording density has been significantly increased. In recent years, a GMR head, a TMR head, or the like has been introduced, and thus the surface recording density has been increased at a rate of approximately 1.5 times per year.
With respect to the magnetic recording medium, there has been a need for further higher recording density to be achieved. Therefore, there has been a need to achieve a high coercive force of a magnetic layer, a high signal-to-noise ratio (SNR), and high resolution. In recent years, an attempt at improving linear recording density and surface recording density by increasing track density has been made.
In recent magnetic recording devices, track density thereof reaches 400 kTPI. However, when the track density in the magnetic recording device is increased, plural pieces of magnetically recorded information between adjacent tracks interfere with each other, and a magnetic transition region of a boundary region becomes a noise source. Accordingly, there is a problem in that SNR deteriorates. This leads to deterioration of a bit error rate (BER), and thus improvement of recording density is hindered.
It is necessary to ensure as large a magnetic saturation as possible in each recording bit and a large magnetic film thickness by making the size of each recording bit on a magnetic recording medium relatively minute so as to increase the surface recording density. On the other hand, when the recording bit is made minute, there is a problem in that the minimum magnetic volume per bit decreases, and thus recorded data may be missed due to magnetic inversion caused by thermal fluctuation.
For example, when the recording density of the magnetic recording medium becomes 2 Tbpsi, an area occupied by one bit is a maximum of 322 nm2 (an equivalent circle diameter of approximately 18 nm), and when considering a mutual operation between adjacent bits, an effective area is narrowed to 193 nm2 (an equivalent circle diameter of approximately 14 nm). With this area, when it is attempted to ensure a particle size capable of maintaining thermally stable data, it is difficult to ensure the number of magnetic particles for maintaining SNR necessary for the magnetic recording device. On the other hand, when the magnetic particles are made minute in order to maintain a SNR of the magnetic recording device, it is difficult to maintain the magnetic data that is recorded due to thermal instability caused by a decrease in volume per magnetic particle.
In addition, in the magnetic recording device, when the track density is increased, a distance between tracks decreases, and thus a track servo technology with a significantly high accuracy is necessary. Therefore, in the magnetic recording and reproducing device, a method is generally used in which data is recorded with a large width and the data is read in a width narrower than during the recording of the data in order to exclude an effect from an adjacent track during reproduction as much as possible. However, in this method, it is possible to suppress the effect between tracks as much as possible, but it is difficult to obtain a sufficient reproduction output. As a result, there is a problem in that it is difficult to ensure a sufficient SNR.
As one method of solving the problem of the above-described thermal fluctuation, and ensuring a good SNR to achieve a sufficient output, an attempt has been made to increase the track density by forming an irregularity along a track on a surface of the magnetic recording medium to physically separate recording tracks from each other (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2004-164692). This technology is generally called a discrete track method. In addition, a magnetic recording medium having a magnetically separated track pattern is called a discrete track medium.
In addition, in order to realize further higher recording density of the magnetic recording medium, a magnetic recording medium is suggested in which an irregularity is also formed for each bit with respect to a longitudinal direction (a circumferential direction) of a track to physically separate magnetic particles from each other and to perform recording with one magnetic particle set as one bit. This magnetic recording medium having a pattern in which both of the spaces between tracks and between bits are magnetically separated is called a bit-patterned medium.
In the bit-patterned medium, when both of the spaces between tracks and between bits are magnetically separated, a magnetic mutual operation that occurs therebetween may be suppressed. Accordingly, stability of recorded data on the magnetic recording medium may increase. In addition, since one bit is constructed by a single magnetic particle, a transition noise caused by a boundary disturbance is suppressed, and thus SNR is improved. As a result, a relatively dense magnetic recording may be realized.
However, when manufacturing a so-called patterned medium such as the above-described discrete track medium and bit-patterned medium, a mask layer having a shape corresponding to magnetic recording patterns is formed on a magnetic layer, and then the magnetic layer is etched by using the mask layer to pattern the magnetic layer to have a shape corresponding to the magnetic recording patterns. Furthermore, a non-magnetic layer is embedded in a portion, at which the magnetic layer is removed, for planarization of a surface of the magnetic recording medium, and then an excess non-magnetic layer and the mask layer are removed.
However, in the method of manufacturing the patterned medium in the related art, the magnetic layer is subjected to a physical irregularity process by using the mask layer, and then the mask layer that becomes unnecessary is removed from the upper side of the magnetic layer by using dry etching or wet etching. At this point, there is a problem in that oxidization or dissolution of the magnetic layer occurs, and thus the magnetic characteristics deteriorate. Therefore, a method of removing the mask layer which is capable of suppressing magnetic damage on the magnetic layer has been required.
The invention has been made in consideration of the above-described circumstances in the related art and an object thereof is to provide a method of manufacturing a magnetic recording medium which is capable of manufacturing a magnetic recording medium that has excellent magnetic separation performance of magnetic recording patterns by removing a mask layer formed on the magnetic layer without causing magnetic damage to the magnetic layer with high productivity, and a magnetic recording and reproducing device that uses the magnetic recording medium manufactured by the method and that is capable of further improving electromagnetic conversion characteristics.